1) Field of the Invention
The invention relates to aqueous dispersions, containing aminooxy crosslinking agents, of copolymers containing carbonyl groups, to processes for the preparation thereof and to the use thereof as a crosslinking system in binders, adhesives and coating agents.
2) Description of the Related Art
Aqueous dispersions based on copolymers which contain carbonyl groups and contain polyhydrazides or polyhydrazones, lead to the formation of highly crosslinked films during the film formation as a result of the chemical reaction between the carbonyl groups of the cohydrazides or polyhydrazones. Such crosslinking systems have been disclosed, for example, by DE-A 1,495,706 (U.S. Pat. No. 3,345,336) or EP-A 15,644 (U.S. Pat. No. 4,256,809).
Due to the good adhesion properties, such copolymer dispersions which crosslink on film formation are used as binders (DE-A 3,319,239=EP-A 130,336), adhesives (EP-B 148,386 =U.S. Pat. No. 4,609,420, DE-A 3,319,240=U.S. Pat. No. 4,529,772), sealing compounds (DE-A 3,537,099) and coating agents (DE-A 3,724,369 U.S. Pat. No. 4,8941261). A disadvantage is, however, the unsatisfactory strength of the adhesive bonds on storage in water.
A further disadvantage of these crosslinking systems is the release of highly toxic and carcinogenic hydrazines during the storage and use of such systems. In EP-B 3,516 (U.S. Pat. No. 4,250,070), DE-A 2,819,092 (U.S. Pat. No. 4,267,091) and DE-A 3,216,967, it is therefore proposed to add water-soluble transition metal salts to the polyhydrazine-containing copolymer dispersions, in order to reduce the content of free hydrazine.
DE-A 3,241,829 (U.S. Pat. No. 4,546,078) has disclosed a process for the immobilization of microorganisms, the microorganisms being suspended in an aqueous solution of an acrolein/vinylpyrrolidone copolymer. After the addition of an aqueous solution of an alkylenedioxydiamine compound, the microorganisms are enclosed in the immediately forming, gel-like polymer mass.
It is an object of the present invention to provide aqueous dispersions which are based on dispersions, containing carbonyl groups, with crosslinking agents and which crosslink on film formation, but with which no release of hydrazine or at least a lower release of hydrazine than in the case of the polyhydrazine crosslinking agents mentioned in the state of the art. Moreover, the crosslinking should proceed only at temperatures of.gtoreq.about 10.degree. C., preferably.gtoreq.room temperature. Additionally, the systems should also have a high storage stability coupled with a high degree of crosslinking during the film formation. The adhesive bonds produced with the dispersions should be resistant to water or organic solvents.